Ok... the two things I would check is how much memory you are giving to using this program and how much quality you are asking from your computer. Both are computer settings, not site settings.

Start
Control panel

System
Advanced

Performance....
performance options:
what are your settings for as windows sees fit? for programs? for appearance?
then
advanced under performance options:
memory usage... what is your priority?
virtual memory...do you need to increase this amount to cover the programs you want to run?